Hybrid drives are known. Hybrid drives have multiple drive sources that may be operated by a range of different energy sources.
For example, methods of combining an internal combustion engine with at least one electric motor are known. In this case, the crankshaft of the internal combustion engine and the drive shaft of the at least one electric motor are connected as input shafts to a gear system (shift mechanism). The internal combustion engine and/or the electric motor are mechanically linkable to an output shaft of the hybrid drive by operating the gear system. The output shaft is used in the known manner to drive a motor vehicle. In particular, hybrid systems that include more than one electric motor are also known.
In this case, in particular, motor vehicles having power branching hybrid drives are known, which, in addition to an internal combustion engine, include two electric motors that may be both motor-driven and generator-driven. Motor vehicles having hybrid drives of this type do not need to include a separate starting system for the internal combustion engine. The internal combustion engine may be started by the at least one electric motor of the hybrid drive by connecting the latter to an energy source, usually the motor vehicle battery. When the at least one electric motor is operating in motor mode, the internal combustion engine is started by shifting the gear system accordingly.
The disadvantage of the known hybrid drives is that the internal combustion engine does not start if the power supply for the at least one electric motor has failed.